I would like to calibrate my understanding of the Book module/blurb with respect to color managementAfter reviewing this forum and the blurb site this is what I understand:

1. Send Book to Blurb converts the images to sRGB, the "preferred RGB" color space for blurb.2. Soft proofing should be done in sRGB rather than using the blurb color profile, which is probably not that reliable for different printer/papers.3. There is no way to in LR to select another workspace

Did I get that right?

That being said, why wouldn't blurb accept any of the other color spaces? What happens if a PDF is sent with Adobe color space?

soft proofing should be done in the output space, not in sRGB. sRGB is not an output space, and Blurb simply follows standard procedures for most requiring sRGB for submitted work to avoid issues with incorrectly tagged images. This means they assume the image is sRGB whether it is tagged sRGB or is untagged. This works fine because the gamut of their presses is easily contained inside the gamut of sRGB. The image will be converted to the indigo press output space before being sent to the press, which is why you want to soft proof with this space.

Lightrooms "space" is irrelevant. The working space doesn't really affect any of this.

So soft proof them in the blurb output space, then output them as jpeg sRGB files to submit to blurb.

I would like to calibrate my understanding of the Book module/blurb with respect to color managementAfter reviewing this forum and the blurb site this is what I understand:

1. Send Book to Blurb converts the images to sRGB, the "preferred RGB" color space for blurb.2. Soft proofing should be done in sRGB rather than using the blurb color profile, which is probably not that reliable for different printer/papers.3. There is no way to in LR to select another workspaceDid I get that right?

Yes and so now you can just about forget soft proofing. For one, LR can't support CMYK profiles and that's the process used for output. Blurb does provide a single profile that they want us to believe defines all their printing processes, papers etc. Forget about that. You have no control over rendering intent which is image specific nor do we know if the conversion they use will support Black Point Compensation. So it's a totally silly color management 'workflow' if I can be so kind to use the term. Might as well just forget about soft proofing in Photoshop which supports CMYK profiles let alone LR which doesn't.

There are ways to make an RGB profile that could soft proof a CMYK process but since Blurb doesn’t provide the actual profiles used to convert the data, it's moot. Note too, they use a different print process for the cover versus the inside of the books. So more disconnect in terms of a proper color management workflow. Send them the book, hope for the best (which in my case, wasn't so good).

Not my experience.Whilst there may not be a full and perfect proofing standard to work to with Blurb, soft proofing to sRGB will highlight any serious issues and prevent a lot of surprises. The presses used for photo books in Europe seem pretty consistent and the HP Indigo profile Blurb suggest using will give a very good idea of what to expect.

The main thing that seems to trip up people is the problem of getting true blacks. An sRGB 0,0,0 won't seamlessly match with a 'Black' applied as a page background in CMYK, so dark images might not melt into the page as expected.

Not my experience.Whilst there may not be a full and perfect proofing standard to work to with Blurb, soft proofing to sRGB will highlight any serious issues and prevent a lot of surprises.

Well based on the years I've used color management, and based on my understanding, that doesn't make sense.

The sRGB color space is one based upon a synthetic color space based on an emissive CRT with defined phosphor's and ambient condition. It has no relationship to the CMYK output color space being sent to the printer. Any more than Adobe RGB (1998), Melissa RGB (which is what you see anyway in LR) or ProPhoto RGB.

Less farther away but just as bogus is the profile Blurb provides which when examined shows it's a GRACoL2006 Coated1. Even if we are to believe they've setup all the Indigo's and whatever press is used for the cover, to emulate GRACoL2006 Coated1 within a decent dE (say a max of dE5), what about all the differing paper's offered. And what rendering intent do they force on every image and using BPC or not?

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An sRGB 0,0,0 won't seamlessly match with a 'Black' applied as a page background in CMYK, so dark images might not melt into the page as expected.

The idea that soft proofing on a display (which can't be set for a contrast ratio based upon the one output device a profile describes), the inability to use the Simulate paper and ink preview isn't proper soft proofing!

The sRGB soft proof idea seems more like a soft proof placebo. There are those on the opposite camp that dismiss soft proofing because it will never appear 100% like the print (an emissive display can never match a reflective print). That camp fails to accept that a 95% match is better than a 80% match. All the various figures can waver depending on how effective the actual color management workflow is and where the weakest link lies. The just send sRGB workflow is great for consumers who wouldn’t know an ICC profile if it hit them in the face. Blurb from LR doesn't seem to fit that mold. Least we forget you can if you so desire, download an actual ICC profile for a device that resides in a specific Costco store. You could actually soft proof and convert you image for output at that actual store.

According to blurb, sRGB is the "preferred" color space. The implication is that other color spaces will be accepted but are not ideal. If we Send Book to Blurb via LR, I suppose there is no choice but to use sRGB. But what happens if a book is submitted directly to blurb outside of LR using - say- Adobe RGB? Does blurb convert to sRGB? Does it even know that the images have been sent with Adobe?

If anything in this thread doesn't make sense it's your earlier comment "you can just about forget soft proofing".

The quote is incomplete. Just forget about soft proofing, using sRGB to Blurb. It's a complete waste of time. It shows you nothing useful.

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If Blurb ask for sRGB images, what reason is there not to soft proof to that colourspace ?

The idea behind soft proofing is to simulate on screen, the output process before you output the document. You are sending your data to a CMYK device. You don't have a profile for that device in this case, the Blurb CMYK profile doesn't define their output(s). Using sRGB is even farther from the truth. Viewing a sRGB soft proof going to a CMYK device doesn't tell you anything about that output. And as I said, any soft proof that voids the use of the simulation of ink and paper is an incorrect soft proof unless you've properly calibrated your display for that by controlling the contrast ratio (few displays can do this).

In LR, you're viewing in an RGB working space anyway, the idea to switch to sRGB somehow tells you something useful in it's preview based on a CMYK process is about as ineffective as loading an Epson 3880 Luster profile when you're printing to a Canon ipf5000 on their glossy paper. Why would you ask LR or Photoshop to show you a complete lie in the preview of a soft proof that has no bearing on the output?

You pick the output profile you will use to convert that data going to the output device for soft proofing. Period. You have to also examine the effect of the Rendering Intent and the paper and ink simulation. That is how you view, on-screen, the image as it will appear (as close as our technology allows) on the output device. The sRGB color space has no role here (even on the Web outside your system).

If you want to get picky, you should be aware that by the time the CMYK conversion process is to start, sRGB (any RGB) is out of the picture, the data will be in Lab. You could just have picked ProPhoto or ColorMatch RGB and the 'soft proof' would be just as incorrect, a lie about the output as if you picked sRGB.

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According to blurb, sRGB is the "preferred" color space. The implication is that other color spaces will be accepted but are not ideal. If we Send Book to Blurb via LR, I suppose there is no choice but to use sRGB. But what happens if a book is submitted directly to blurb outside of LR using - say- Adobe RGB? Does blurb convert to sRGB? Does it even know that the images have been sent with Adobe?

In LR, you're exporting sRGB to Blurb. FWIW, in Aperture it's Adobe RGB (1998) going to their CMYK printers. IF they tell you they can take any RGB working space, it means their front end is smart enough not to assume sRGB (that's good) and they will convert to the output color space from any tagged RGB space. Unlike many silly RGB lab's out there, they will allow you to send them something other than sRGB. Blurb doesn't, as these other labs do, assume and demand sRGB. But when rubber hits the road, whatever RGB working space you provide will play a small role, mainly in terms of out of gamut colors in the source that could be mapped to the destination (yet again, you have no idea what rendering intent or in this discussion profile will be used to end up in CMYK).

Bottom line: IF you have a service provider that demands sRGB, soft proofing is hardly useful assuming they give you a generic CMYK profile that doesn't define the output fully. Soft proofing to a CMYK device using an RGB working space based on a CRT is just a waste of time, it shows you nothing that has any bearing on the output in terms of a soft proof. Might as well just view the image in it's current RGB working space.

If you have service provider that demands sRGB and a profile they will use for the actual output, and they let you use it fully, that is now very useful as you control the process and presumably (short of using a device link which seems unnecessarily), they will send the CMYK numbers as is, to the press. The data you converted and saw is the data sent to the printer.

For this to work, the display calibration and profile and the print viewing conditions have to be configured correctly. It's 'diffcult' enough doing this to a high degree with the correct output profile. Using a profile that has no bearing on the output and thus the soft proof is just a soft proof that has nothing useful to show you.

So why not proof to that space ?Are you suggesting that the differences between Melissa RGB and sRGB aren't worth considering ?

It is an intermediate color space that has absolutely nothing to do with the output device which is in CMYK. You could send them Lab and that would be the case as well. At least that's a device independent color space not that it helps in soft proofing to an undefined output color space.

Have you ever seen the differences between say sRGB and a CMYK output device like an Indigo in 3d?

Yes, the differences between Melissa RGB (which is used for numbers, not the color space you're viewing, that depends on the modules and other factors) and sRGB are not worth considering in terms of the soft proof.

Yes, the differences between Melissa RGB (which is used for numbers, not the color space you're viewing, that depends on the modules and other factors) and sRGB are not worth considering in terms of the soft proof.

If it's not worth trying to soft proof to sRGB, why did Adobe build in the facility ?

If it's not worth trying to soft proof to sRGB, why did Adobe build in the facility ?

You should always have the ability to soft proof to another RGB working space. I'm working in ProPhoto and I want to see what that image would look like IF I convert to that color space. Get it? You load the profile for a soft proof based on what you want it to simulate. You're printing to a CMYK device. You're not sending the Blurb book to the web (on your system). There is zero reason to soft proof to sRGB. It isn't the output color space.

There is zero reason to soft proof to sRGB. It isn't the output color space.

Well sRGB IS the space output from your system to Blurb and it IS different to the default space the images are in when being viewed in LR.

No, it's not the final printed output space, but it makes sense to me to least take an interest in what the files you send to Blurb will actually look like leaving LR, even if it's not the most perfect proof view that might be possible for the final printed product.

Just throwing your hands in the air and saying nothing is worth doing isn't very helpful when there are tools available that at least help to spot problems before publishing.

Andrew, you seem to know a lot about how Blurb works. Please tell me if the procedure below might get you decent soft proofing.

First, order a book with the cover and paper selections that you'll use in the real book. Make the images in the book color patch sets like this one (not very artistic, but useful for characterizing their printing process). Pick a supported RGB color space for the target, one that is big enough to encompass the printer gamut, but not so big that the eight-bit-per-color-plane encoding causes problems.

When you get the book, cut the pages out and scan them with a spectrophotometer, then make profiles for the pages and the cover.

Use those profiles for soft proofing.

When you export from LR, use the color space that you used for the targets. [Correction: export in the color space of the profile that you created, so it can control the gamut mapping. Then assign the profile of the supported RGB color space you used for the target, but don't change the data.]

I can see some potential problems with this approach. What if Blurb does image-dependent processing on what you send them? What if the send your images to different presses with different characteristics depending on their internal operational needs? What if they don't calibrate the presses to some invariant standard?

Still, it might be better than nothing, assuming you're ordering enough books to make it worthwhile to go to all that trouble.

If their process is stable, then others could use the profiles you developed, given that the license that you bought for your profile maker lets you distribute the profiles.

You can't build a profile for Blurb without sending them the correct (CMYK) targets and by having an understanding of the front end and how it deals with untagged CMYK. You need to know (or work though lots of output) GCR, total ink, linearization based on lpi and a host of other stuff only Blurb knows.

You can't build a profile for Blurb without sending them the correct (CMYK) targets and by having an understanding of the front end and how it deals with untagged CMYK. You need to know (or work though lots of output) GCR, total ink, linearization based on lpi and a host of other stuff only Blurb knows.

Andrew, if these are all point processes, why can't we calibrate them out in the profile-making process? The way I see it, the situation is similar to making a profile for an Epson printer. The printer is a CMYK device (or a CcMmYKlKllKGO device, in the case of the x900 printers) but the driver wants RGB input. I build a profile for that printer by feeding it RGB targets and seeing what colors come out. The printer driver can do all the under color removal, gray component replacement, ink limiting, etc. it wants, as long as it does it the same for every RGB triplet, and it does it without discontinuities that render the three-D by three-D trilinear interpolation unacceptably inaccurate.

But maybe I'm missing something. At the conceptual level, what's the difference between and Epson 4900 and the Blurb liquid electrophotographic printers?

There are at least two ways you could build an RGB profile just to soft proof Blurb within LR. We need the profile that actually defines the process, then build a ColorCast profile in ColorThink Pro in RGB which one could load to soft proof. You can't convert of course. And you still have to force a rendering intent on every image on the receiving end. Sending out the RGB targets to build an RGB profile just for soft proofing could work nicely and it is way better than using sRGB! The TAC, GCR settings wouldn't affect the soft proof much if at all. Minor tweaking for a match could be done in an display specific setting and profile.

Now that you have this RGB soft proof profile, how does the actual press behavior vary over say a month? How close does the calibration bring it back to the measured target? Ideally you'd send that target out X number of times over a month (I'd prefer 2-3 a day). You'd see how it varies over average and max dE among other metrics,and then use that average data to build the profile again for soft proofing.

Now that you have this RGB soft proof profile, how does the actual press behavior vary over say a month? How close does the calibration bring it back to the measured target? Ideally you'd send that target out X number of times over a month (I'd prefer 2-3 a day). You'd see how it varies over average and max dE among other metrics,and then use that average data to build the profile again for soft proofing.

Andrew, you're right about all that. Who knows how stable the process is? You'd think hp would have built in some calibration features, and maybe they have, but I don't know what they are. I'd try it and post the profile, but my license to the profile making software I use won't let me do that, so this idea may remain a gedanken experiment. I'm not planning on printing any books in the near future, so it's not worth it to try it for myself.

As a side point, the marking engine of most of the hp Indigo line has seven toner stations. I don't know how many Blurb uses, but, if they use them all for process colorants, profiling in colorant space could be complicated.